Charge pumps can be used in electrical circuits where a circuit element may continuously or temporarily need a supply voltage being larger than a usual voltage provided to supply the circuit. Especially as modern circuits become more power-efficient by reducing the supply voltage for the majority of the circuit elements, such charge pumps become more important. As an example, in the field of MEMS microphones with a MEMS capacity in a MEMS chip and with an electrical signal evaluation circuit in an ASIC chip, supply voltages of 1.2 V or below become popular. However, such a supply voltage for a signal amplifier is critical and may lead to distortion problems, especially when a large amplifier gain is required.
Negative charge pumps are known from U.S. Pat. No. 8,830,776.
Negative charge pumps have been used in many ASICs. However, many negative charge pumps need an electrical potential below a reference potential for their own power supply. Such a charge pump is known from U.S. Pat. No. 7,145,318.
Another charge pump is known from the article “A 40 nm fully integrated 82 MW stereo headphone module for mobile applications”, IEEE Journal of Solid-State Circuits, Vol. 49, No. 8, 2014. However, this charge pump needs a large volume holding capacitor to store charge to maintain a negative output potential which makes a monolithic integration in an ASIC chip difficult.
Thus, what is needed is a negative charge pump that can replace previously used negative charge pumps in electrical circuits to avoid the need to redesign the known circuits.